The production of beta-lactamase (penicillinase) enzymes by bacteria is an important factor in bacterial resistance to penicillin therapy. Despite considerable effort, no general inhibitor of these enzymes is yet available. Progress towards the development of such an inhibitor is likely to come at this stage only from an understanding of the mechanism of action of these enzymes, which at present is almost completely lacking. The objective of the proposed research then is to investigate the details of penicillinase catalysis by means of pre-steady state kinetic studies. The conformational flexibility around the active site of these enzymes, apparently an important factor in their specificity, will also be studied by these means. It is further proposed that the use of fluorescent substrates and modified enzymes will allow, by energy transfer measurements, useful estimates of protein motion during catalysis to be obtained; this work then should be of considerable fundamental interest also. The intriguing question of alternative substrates and the biological role of the beta-lactamase enzymes will also be examined as part of this work.